spi: fix a typo inside a kernel-doc markup

spi_split_tranfers_maxsize -> spi_split_transfers_maxsize

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/a103f4f48735caa1a09fad94c5d76e73e2ce37b8.1603469755.git.mchehab+huawei@kernel.org


Signed-off-by: Mark Brown <broonie@kernel.org>